The present invention is directed generally to three-point hitches such as those commonly found on agricultural tractors, and more particularly to an improved three-point hitch upper arm including a powered adjuster for automatically and precisely adjusting the length of the upper arm.
With a conventional three-point hitch, an implement tool bar is supported at three points by a pair of spaced-apart lower arms and a central and higher upper arm. The lower arms, of course, are pivotally raised and lowered either by hydraulic cylinders or by lift arms connected to powered cranks on the back of a tractor. Whereas the lift arms control raising and lowering of an implement between its working and transport positions, the length of the upper arm is adjusted to fit the angle of the implement in its working position.
The adjustment of the length of the upper arm is critical in certain operations such as plowing wherein the plow must "suck in" to one side to operate properly. If the front-to-back inclination of the plow is not just right, it will not operate effectively. Accordingly, a farmer would normally attach the implement to the tractor three-point hitch and simply eyeball the length of the upper arm to what he thinks is the right adjustment and then proceed across a field a short way, stop the tractor, get out and manually adjust the length of the upper arm by applying a wrench to the turnbuckle collar, then climb back aboard the tractor and do the same thing again until the implement is just right. Particularly with the new large tractors, constant mounting and dismounting of the tractor is a terribly exerting and inconvenient manuever.
It has previously been known to substitute a length adjustable hydraulic cylinder in place of the conventional turnbuckle for the upper arm or middle length of the three-point hitch connection to an implement. It is difficult, if not impossible to precisely control the extension and retraction of the cylinder, however, since it occurs in somewhat jerking steps of unpredictable length. This type of powered link is therefore generally unacceptable for applications where precise adjustment is required.
Accordingly, a primary object of the invention is to provide an improved powered adjuster for a three-point hitch upper arm.
Another object is to provide a powered adjuster capable of precisely controlling the extension and retraction of the upper arm length.
Another object is to provide such a powered adjuster having means for identifying selected positions thereof whereby the upper arm may be readjusted to a selected position without further experimentation.
Another object is to provide such a powered adjuster which is adaptable for use with the pair of male threaded connection members of a conventional turnbuckle style upper arm.
Another object is to provide such a powered adjuster for a three-point hitch upper arm which is simple and rugged in construction, economical to manufacture and efficient in operation.